Microtome knife sharpener



,1970 A. J. CAMPBELL I 3,546,819

MICROTOME KNIFE SHARPENER Filed Oct; 17, 1968 2 Sheets-Sheet l Arrow/215 United States Patet 3,546,819 MICROTOME KNIFE SHARPENER Andrew J. Campbell, San Mateo, Calif assignor to The Regents of the University of California, Berkeley, Calif. Filed (Pet. 17, 1968, Ser. No. 768,328 Int. Cl. B24b 9/00 US. CI. 51-73 8 Claims ABSTRACT OF THE DISCLOSURE A microtome knife sharpener has a glass cylinder mounted above a magnet and on a pair of frame-supported rollers. The cylinder is driven in either direction to rotate about a horizontal axis and has liquid-confining rings at both ends. If desired, the magnet can be moved in a path having an axial component.

Under many circumstances and particularly for the preparation of scientific specimens, there is employed a cutting arrangement generally referred to as a microtome that utilizes an accurately sharpened knife for the cutting function. The preparation or sharpening of such knives is a matter of some difliculty since it is necessary not only to achieve extreme sharpness, but it is likewise advisable to sharpen the cutting edge in a line substantially parallel to the back or thickened edge of the microtome knife.

It is therefore an object of the present invention to provide a machine which is effective to afford a satisfactory sharpening operation on a microtome knife.

Another object of the invention is to provide a machine which will afford a microtome knife sharpened edge substantially parallel to the thickened back edge of the knife.

Another object of the invention is to provide a microtome knife sharpener which can accommodate a number of microtome knives at one time.

A further object of the invention is to provide a microtome knife sharpener in which the knife being sharpened is maintained in appropriate attitude for optimum sharpenmg.

A further object of the invention is to provide means for sharpening a microtome knife with some movement of the knife along the edge in order to assure a uniform result.

A further object of the invention is in general to provide an improved microtome knife sharpener.

Other objects together with the foregoing are attained in the embodiments of the invention described in the accompanying description and illustrated in the accompanying drawings, in which:

FIG. 1 is an elevation of a microtome knife sharpener constructed pursuant to the invention;

FIG. 2 is a detail cross-section to an enlarged scale, gileGplzllne of section being indicated by the line 22 of FIG. 3 is a side elevation of a microtome knife sharpener constructed pursuant to the invention, a portion being broken away to disclose the interior construction primarily on a vertical longitudinal plane;

FIG. 4 is a cross-section in detail to an enlarged scale, the plane of section being indicated by the line 44 of FIG. 3;

FIG. 5 is a cross-section on a longitudinal vertical plane of a portion of a modified form of microtome knife sharpener, portions of the figure being broken away to reduce its size;

FIG. 6 is a cross-section, the plane of which is indicated by the line 66 of FIG. 5;

FIG. 7 is a cross-section, the plane of which is indicated by the line 7-7 of FIG. 5; and

FIG. 8 is a side elevation of a modified form of supporting roller with its immediate environment and with a portion of the figure shown in cross-section on a radial plane through the axis of the roller.

As particularly illustrated in FIG. 4, a typical microtome knife is substantially a wedge-shaped strip of metal 6, usually steel, having a relatively heavy cross-section and terminating in an edge 7 which it is desired to have as sharp as possible. The edge 7 is defined between a pair of converging side edges 8 and 9, each of which is substantially planar, although there may be some concavity in some designs.

Pursuant to the invention, the microtome knife sharpener includes a frame 11 within an enclosing housing 12 and supporting, by means of journals 13 and 14, a pair of rollers 16 and 17. The rollers are arranged as shown in FIG. 1 with their axes parallel to the length of the frame and parallel to each other. Each of the rollers includes a central, circular cylindrical body 18 and incorporates a pair of end flanges 19 and 21. Both of the rollers carry pulleys 22 at one end with a belt 23 trained over the individual pulleys and also trained over a driving pulley 24 on the reduction shaft 26 of a drive motor 27 mounted on the base 11. When the motor is energized, both of the rollers 16 and 17 are rotated in the same direction.

Adapted to rest by gravity on the rollers and to be con tained well within the housing 12 is a cylindrical 31. This is preferably a tube of glass arranged with its longitudinal rotational axis 32 parallel to the axes of the rollers 16 and 17. The member 31 is defined by a circular cylindrical outside surface 33 and a circular cylindrical inside surface 34 and preferably is partially closed at both ends by rings 36 and 37. The interior 34 of the cylinder 31 is made as nearly circular cylindrical as is reasonably possible. In some instances the glass cylinder is ground interiorly, although if carefully made it can be molded to an appropriate dimension. The cylinder is not necessarily glass since it can be of other materials which are magnetically permeable, but it is now preferred to utilize glass since it is not only magnetically permeable but is likewise unaffected by many of the liquids or gases which sometimes are in the vicinity of the sharpener.

Supported on the frame 11 just below the cylinder 31 is a magnet 38 usually of a flat, rectangular form and disposed near the lower periphery of the cylinder 31, so that the field of the magnet penetrates the glass cylinder and extends into the interior thereof.

In the use of this device, there is provided within the cylinder 31 to a level not exceeding the radius of the rings 36 and 37 a bath 41 made up of a convenient liquid and grit of a predetermined fineness. A microtome knife is introduced by hand through the open end of the cylinder 31 and is permitted to come to rest by gravity on the bottom of the interior surface 34 of the cylinder in the vicinity of the magnet 38. If the microtome knife is substantially as long as the cylinder, only one unit can be accommodated at one time. However, if the microtome knives are relatively short, two or three can be introduced simultaneously and located generally in axial alignment. After the blade has been positioned in the bath within the cylinder, the motor 27 is energized. Preferably the motor is under the control of a hand switch 42 situated on the front of the frame 11 and having a forward position 43 and a reverse position 44 as well as a central off position, as illustrated.

Preferably there is provided a timer 46 on the frame 11 so that if desired the time period during which the switch is effective can be regulated. The switch is moved into its forward position and the motor then drives the cylinder 31 in the direction indicated by the arrow 46 in FIG. 4. The motion of the cylinder tends to displace the microtome knife slightly in the direction of the arrow 46,

but the Weight of the microtome knife retains it substantially in the lowermost position. This alone is effective under many circumstances and the magnet 38 can often be dispensed with, but in the present case the magnet 38 is effective also to urge the microtome knife toward the interior surface 34 of the revolving cylinder. The grit in the bath in passing between the cylinder surface and the microtome knife effects a sharpening operation. Because of the circular cylindrical nature of the member 31, the edge 7 is sharpened and contoured to be almost exactly parallel to the other edge of the microtome knife.

At the conclusion of one sharpening operation, the switch 42 can be reversed, if desired, so that the cylinder turns in the direction of the arrow 47 in FIG. 4. The reverse direction of operation is preferred sometimes for certain sharpening operations, and the discretion of the operator can be utilized to select the direction of operation or for alternate operations.

The microtome knife itself can be reversed in position as shown by the dotted lines in FIG. 4 and after a predetermined period is usually inverted so that the previously upper face becomes the lower face and the other side of the edge is itself sharpened. The same techniques are employed for sharpening the other side of the knife edge.

During the sharpening operation, perhaps due to slight inaccuracies in the shape of the cylinder or perhaps due to slight inaccuracies in the linearity or parallelism of the microtome knife, the knife tends to move in an axial direction toward one end or the other of the rotating cylinder. This movement is beneficial and desired. It is arrested only by the abutment of the axially moving microtome knife against one of the rings 36, which serves not only, therefore, as a retainer for the liquid-grit bath but also as a buffer for any migrating microtome knives. The effect of the magnet 38 does not preclude this axial movement of the microtome knife.

At the conclusion of one phase of the sharpening operation, the treated microtome knives can be removed by hand from the bath and withdrawn from the sharpener. The bath can then be removed and replenished with a bath containing finer grit, or the withdrawn knives can be advanced to another similar sharpener having a bath with finer grit in it. In fact, several meshes of grit can be utilized in the progressively finer sharpening of the microtome knives. In any event, at the conclusion of the set time or as desired by the operator, the mechanism is turned off and the operation is concluded.

In some instances it is preferred to induce an axial movement of the microtome knives being sharpened rather than to rely on any random axial movement. For that reason, the rest of the mechanism remains substantially the same except that the frame 11 (FIG. 8) instead of carrying continuous rollers 16 and 17 is provided with substitute rollers 51 which are substantially identical to each other. Each includes a central shaft 52 on which roller segments 53 are individually mounted and held by set screws 54. The drive is preferably by belt to a pulley 56 in the center and held by a set screw 57 on the shaft 52. Collars 58 and 59 are disposed at the ends of the shaft 52 by fasteners 61 and 62.

Resting on the rollers 51 is a glass cylinder 63 which in this instance instead of having separate rings 36 is pro- 4 in bearings 72 and 73. The shaft 71 carries a pulley 74 around which a belt 76 is trained, the belt leading to the motor 27, as does the belt from the pulley 56.

Engaging pulleys 77 and 78 on the shafts 69 and 71 is a belt 79 arranged in an elongated race track contour. At one point the belt carries an upright pin 82 at its upper end slidably seated in a transverse slot 83 formed in a reciprocating block 84 confined between channels 86 and 87 mounted on the frame 11. The block 84 has a dovetail connection with a permanent magnet 88.

Whenever the motor 27 is driven, not only are the rollers 51 rotated, but likewise the pin 82 follows a race track path and soaxially reciprocates the magnet 88. While the magnet 88 and the magnet 38 are preferably permanent magnets, they can without difficulty be replaced by electromagnets, and in the case of a moving magnet the leads are made flexible.

In the operation of this device, the microtome knife or knives are deposited in the bath 68 containing grit as before, and the motor is energized not only to rotate the cylinder but likewise to reciprocate the magnet 88. The microtome knives are thus not only given the effect of the circumferential grit abrasive action as before, but likewise get an axial effect as the knives are positively moved to and fro in an axial direction. This is because the magnetic field of the magnet which penetrates the glass of the cylinder moves to and fro and carries the magnetically responding knife or knives with it. The directions as to reversing the knives and timing of the sharpening step are precisely as before. At the end of the operation eachv microtome knife is found to have been sharpened to an exceedingly fine cutting edge with that edge substantially parallel to the opposite edge of the knife.

What is claimed is:

1. A microtome knife sharpener comprising a frame, a magnetically permeable cylinder having an inner surface for slidably engaging a knife to be sharpened, means for supporting said cylinder on said frame for rotation about a horizontal axis, means on said frame for rotating said cylinder about said axis, and a magnet on said frame in position to establish a field of magnetic force within said cylinder to maintain said knife in engagement with said inner surface.

2. A microtome knife sharpener as in claim 1 including means for retaining a body of liquid within said cylinder.

3. A microtome knife sharpener as in claim 2 in which said retaining means includes rings within both ends of said cylinder.

4. A microtome knife sharpener as in claim 1 including means for constraining said cylinder against axial translation on said frame.

5. A microtome knife sharpener as in claim 1 in which.

said rotating means is effective to rotate said cylinder se-.

to each other and parallel to the axis of said cylinder.v

8. A microtome knife sharpener as in claim 1 in which said cylinder is glass.

References Cited UNITED STATES PATENTS 2,807,020 9/ 1957 Schell 51-28 1 FOREIGN PATENTS 331,081 10/1935 Italy.

OTHELL MPSQN, Pr ma y Examiner 

